The G2 weekly recipe: Turbot baked in salt with clams and leeks

This is the purest way I know of cooking fish. The brilliantly white flesh cooks solely in its own juices. Any fine flat white fish - halibut or brill for example - will do, but according to Nick Wilson of Cape Clear Fish Shop, there's some affordable and excellent quality farmed turbot coming from Anglesea now. Nick deserves a mention as he is a brave man, having opened a fishmongers (and not a ridiculously priced uber-posh one) pretty much on the front step of a huge Tesco. When I was little there were three fishmongers within walking distance of our house, then suddenly there were none. We need more Nicks.

Serves 6

A 2kg turbot, gutted and cleaned

4 fresh bay leaves

20g parsley (leaves roughly chopped, stalks whole)

20g thyme (½ on the stalks and ½ leaves)

4 garlic cloves, peeled, 2 sliced, 2 chopped

2.5-3kg coarse rock salt

600g leeks, sliced thinly and washed well

70g unsalted butter (room temperature)

2 glasses white wine

500g fresh clams, or mussels

One third of a chicken (or veg) stock cube

100ml double cream

black pepper

Preheat the oven to 220°C/425°F/ gas 7. Stuff the roe cavity (ask your fishmonger to point it out) and gill holes of the fish with the bay leaves, parsley stalks, sprigs of thyme and sliced garlic.

Spread 750g salt on the bottom of a roasting tin large enough to hold the fish. Lay the fish on top and cover with the rest of the salt. The salt crust must be intact, about 1cm thick all over. Sprinkle on a little water - this helps create a total seal when it goes in the oven. Whack in the oven for 30-40 minutes, depending on the size of the fish.

In a large, deep saucepan melt two thirds of the butter and gently fry the leeks, the rest of the garlic and the thyme leaves for 10 minutes with a lid on. Add the stock (use a third of a cube in 600ml water to make a light stock) and reduce by two thirds. Then add the wine and clams and, with the lid on, bring back to simmering point. Have a taste to see how gritty your molluscs are: if it's a bit dredgy in there, transfer the leeks, cockles, thyme and garlic to a clean pan and then strain the stock to get rid of any grit. Stir in the cream and parsley leaves. Turn the heat off and put the lid back on.

Remove your fish from the oven. Using the back of a wooden spoon, tap the middle of the mound firmly to break the salt crust. Gently peel and sweep away the salt to the edges of the roasting tin with your best fish slice and ditch it. Carefully remove the skin - it should peel off - and discard. Lightly score along the backbone with a fish slice or palette knife. Using the end of your fish slice scrape out the fin bones which run around the edges of the fish, leaving the clean fillets. Carefully lift off the white flesh in portions.

Stir the remaining butter into the clam mix. Season with black pepper. Serve the slabs of turbot with the juicy clams ladled around. Rather special.

· Allegra McEvedy is co-founder of fast-food chain Leon. Her colour cookbook is published by Kyle Cathie Ltd at £19.99. To order a copy for £18.99 with free UK p&p, go to guardian.co.uk/bookshop or call 0870 836 0875.